Regulation of heart mitochondrial respiration and calcium transport by NO

ZAOBORNYJ T; ALMEIDA AM; SIVAKUMARAN V; O´ROURKE B

Buenos Aires

Congreso; VIII Meeting of the South American Group of the Society for Free Radical Biology and Medicine; 2013

South American Group of the Society for Free Radical Biology and Medicine

The effects of NO on Ca2+ influx were characterized by exposing guinea pig heart mitochondria to NO released from two donors. Mitochondrial NO production, membrane potential and Ca2+ uptake were followed simultaneously using DAF-FM, TMRE, Calcium Green and Fura-FF. Isolated mitochondria O2 consumption was assessed using a XF96 analyzer. State 4 O2uptake was not modified by GSNO or SNAP. The addition of Ca2+ to the medium produced a 20% enhancement in state 4 O2 consumption and this effect was abolished by GSNO or SNAP. Energized mitochondria were submitted to 10 microM Ca2+ pulses up to a final concentration of 80-100 M (200-450 nmol/mg protein), showing no significant alterations in matrix volume and membrane potential. In the presence of GSNO or SNAP (25 to 100 microM), Ca2+ uptake was slower and extramitochondrial Ca2+ concentration increased. When single 50 microM Ca2+ pulses were added, mitochondria treated with NO donors showed a decreased Ca2+ accumulation rate (40-50%) with an IC50 of about 400 microM (180 nM NO). The addition of L-arginine or NOS inhibitors to control mitochondria produced changes in Ca2+ uptake and in DAF-FM signal. These results suggest that Ca2+ and NO act as signals that coordinate cytosolic workload and mitochondrial energy metabolism.